The invention relates to improvements in apparatus for transporting tobacco particles, and more particularly to improvements in apparatus for converting a multilayer stream or flow of tobacco particles into a single layer or carpet of such particles. Still more particularly, the invention relates to improvements in apparatus for converting a continuous stream or flow of tobacco particles into a formation in which all or practically all of the particles are exposed.
As used herein, the term single layer (or monolayer) is intended to denote a flow of tobacco particles (such as strips, ribs and like tobacco fragments) which were obtained as a result of prior treatment and processing of tobacco leaves and are to be transported in the form a stratum wherein at least a large majority of particles are disposed next to, rather than above, each other.
The transformation of a multilayer stream or flow of tobacco particles into a single layer is a prerequisite for satisfactory treatment prior to conversion of the flow into a rod which is normally trimmed to form a rod-like filler ready to be draped into a web of cigarette paper or other suitable wrapping material. The thus obtained wrapped filler is ready to be subdivided into plain cigarettes, cigars or other rod-shaped articles of the tobbaco processing industry.
The treatment of the single layer of tobacco particles prior to conversion into a rod-like filler normally includes or can include sifting, spraying an additive onto the single flow, and particularly scanning for the purpose of detecting and expelling foreign particles including fragments of metal, rock or the like. The scanning normally involves monitoring the single layer with one or more photoelectronic detectors. Detection and expulsion of all foreign particles should be completed at an early stage of tobacco processing in order to ensure that the foreign particles cannot interfere with predictable treatment of tobacco. For example, a fragment of metal or rock is likely to make a hole in the wrapping material and to thus affect the appearance as well as the quality of the ultimate product, such as a plain or filter tipped cigarette, cigar, cigarillo or the like.
Another important prerequisite for satisfactory treatment prior to conversion of a stream of tobacco particles into a rod-like filler is that the single layer should be advanced at a rate which is necessary to satisfy the requirements of modern high-speed machines, e.g., cigarette makers which turn out up to and in excess of 14,000 articles per minute.
If the monitoring of a rapidly advancing layer of tobacco particles is to result in the detection of all or practically all foreign particles, each and every article of the layer should be detectable by an optoelectronic detector. Problems arise if the particles of the layer overlie each other because the subivision of tobacco leaf laminae (i.e., tobacco leaves which were relieved of ribs) results in the making of so-called strips the shape and the dimensions of which often closely approximate or match the shape and size of certain foreign particles. The heretofore known apparatus for the conversion of a continuous multilayer stream of tobacco particles into a single layer wherein satisfactory particles are in random distribution with undesirable foreign particles and all particles can be detected by presently known monitoring devices are incapable of satisfying the above outlined requirements, primarily because a relatively large percentage of particles is overlapped and thus concealed from view by the neighboring particles.